Organic Chemistry 1. Introduction: – Only living materials can produce organic compounds Vital Force Theory – Only – Synthesized urea (organic) from ammonium cyanate (inorganic) Friedrich Wohler – Synthesized Valence - Combining ability of organic compound based on the fixed number of bonds Catenation - Ability of carbon to bond with other carbons – Gaining or Losing electron Ionic Bond – Gaining – Sharing of electrons Covalent Bond – Sharing Formal charge = Group number – ½ shared e - number of unshared e – Molecules represented in different Lewis structure that differ in the positions of e Resonance – Molecules – Optimum distance between the nuclei of two bonded a toms Bond length – Optimum – Energy required breaking the bonding between a pai r of atoms Bond energy – Energy – Angle between two adjacent bonds Bond angle – Angle – Mixing of two or more atomic orbitals to give the same number of new orbitals Hybridization – Mixing Constitutional Isomers – same – same molecular formula but different connectivity of atoms
Higher boiling point: 1. Look for dipole-dipole interaction (higher) 2. Look for hydrogen bonds (higher) 3. Look for higher molecular weight (higher) 4. Look for branching (lower) Functional Group:
2. Acids and Bases: Bronsted Lowry Acids - proton donor – proton acceptor Bronsted Lowry Base – proton Weaker Acids are always favored in equilibrium reaction Acidity Prediction: (ARIO)
-
– electron acceptor Lewis Acid – electron – electron donor Lewis Base – electron
3. Stereoisomerism: – same connectivity but differ in spatial arrangement Stereoisomers – same Enantiomer – mirror – mirror images but not superimposable – four different bonded atoms Chiral center – four – R (to the Right) and S (to the left) enantiomer Cahn-Ingold-Prelog System – R – ability of the molecule to rotate the plane of a plane polarized light Optical activity – ability – positive rotation Dextrorotatory – positive – negative rotation Levorotatory – negative – equal amount of enantiomers in solution Racemic mixture – equal
) (
n
No. of stereoisomers = 2 , n= chirality centers – has multiple chirality centers but still achiral due to symmetry Mesocompound – has 4. General Organic Reactions – Transition state resemble reactant if exergonic(- ΔG) or product if endergonic (+ΔG) Hammond Postulate – Transition Tertiary carbocation are more stable that secondary a nd primary because of hyperconjugation
Electrophiles are reagents which in their reactions seek the extra electrons that will give them stability Nucleophiles are reagents that seek a proton or some other positive center Substitution Reaction:
Concerted Process – nucleophilic – nucleophilic attack and loss of leaving group occurs simultaneously nd SN2 is a concerted process and 2 order kinetics st SN1 is a stepwise process and 1 order kinetics Polar protic solvent favors SN1 Polar aprotic solvent favors S N2
5. Alkanes and Cycloalkanes - also called paraffins or unsaturated hydrocarbons, sp3 hybridized At room temp: C1-C4 – gases C5-C17 – liquids C18- Cn – solids – most stable cyclohexane conformation Chair conformation – most Others: half chair, boat, twist boat
Primary reactions: radical reactions – reaction – reaction with light and heat f orming radicals 6. Alkenes - also called olefins, sp2 hybridized Bredt’s rule rule - eight-membered ring is the smallest size ring that can accommodate a trans double bond in a bridged bicyclic compound Trans is more stable than cis
Elimination Reactions:
E2 (Elimination Bimolecular) -One step mechanism, similar to SN2, Zaitsev is favored E1 (Elimination Unimolecular) -Two-step mechanism, similar to SN1, Zaitsev is always favored Zaitsev product – double bond on the more substituted side – double bond on the less substituted side Hoffmann product – double If the base is bulky , Hoffmann product is favored
Addition Reactions:
7. Alkynes - has triple bonds, sp hybridized - One sigma bond and two pi bonds Addition Reactions:
8. Aromatic Compounds - benzene derivatives - planar - cyclic - follows Huckel’s Rule: 4n+2= pi electron, n is a whole number Bond order of benzene is 1.5 Annulenes – compounds – compounds containing single ring that contains fully conjugated pi electrons
Benzene is also known as [6]Annulene Ortho-Para Director: Strongly activating – N in Amine, O in OH Moderately activating – N attached to carbonyl, O attached to R Weakly Activating – R group, Weakly Deactivating - Halogens Meta Directors: Moderately Deactivating – Cyanate, sulfonate, carboxyl, carbonyl + Strongly Deactivating – Nitro, -NR 3 , -CX3,
Aromatic Substitution Reactions:
Other Aromatic Reactions:
9. Alcohols, Thiols, Sulfides and Ethers – has hydroxyl (-OH) functional group Alcohols – has Ethers – has – has alkoxy (-OR) functional group Thiols – has marcapto (-SH) group Sulfides – has -S-S- group
Boiling Point: Point: Alcohol > Ethers Grignard Reagents- carbon nucleophiles (usually with Mg) that can attack electrophiles Oxirane- three membered ringed ethers Epoxide- substituted oxirane Reactions: Alcohols and Phenols:
Ethers, Thiols, and Sulfides
10. Aldehydes and Ketones - contains carbonyl group - soluble in water Reactions:
11. Carboxylic Acids and Derivatives - contains Carboxyl group (-COOH) Gilman Reagent – lithium – lithium aluminum dialkyl cuprate Fischer Esterification – carboxylic – carboxylic acids are converted to esters by reacting with alcohols with acid catalyst – Hydrolysis of esters in basic condition to form carboxylic acids Saponification – Hydrolysis Reactions:
12. Amines - contains amino functional group (-NH 2) o
o
o
Basicity: 2 > 1 >3 > Amine Reactions:
